A JWST NIRCam/MIRI view of the W51A high-mass star-forming region

TL;DR

This paper presents high-resolution JWST NIRCam and MIRI observations of the W51A high-mass star-forming region, revealing detailed structures, feedback effects, and protostellar activity, advancing understanding of massive star formation processes.

Contribution

First detailed JWST NIRCam and MIRI imaging of W51A, highlighting novel features and providing insights into feedback and protostellar jets in a high-mass star-forming region.

Findings

Resolved dust filaments feeding W51-E

Detected a protostellar jet impacting dense medium

Identified only 10% of ALMA sources with JWST

Abstract

We present observations of the W51A region, including the massive protoclusters W51-E and W51-IRS2, with JWST in 10 NIRCam and 5 MIRI filters. In this work, we highlight the most novel features apparent in these images and compare them with other multi-wavelength images. The broad view of the NIRCam/MIRI images of the W51A region shows that areas dominated by warm dust and ionized gas are distinct from those dominated by PAHs. The high angular resolution of the JWST images resolves dust filaments in high contrast, revealing geometrically converging features feeding W51-E and a cavity around W51-IRS2. This picture adds support to the hypothesis that feedback from W51-IRS2 is suppressing further gas infall onto the protocluster, while by contrast, gas is still accreting onto W51-E. Comparing the NIRCam and MIRI images to ALMA data, we find 24 sources detected by both JWST and ALMA, accounting for only $\sim10\%$ of the ALMA sources; the rest are too embedded or too cool to be detected by JWST. A knot of [Fe II] and H$_2$ emission north of W51-IRS2, previously detected in ground-based images, reveals peculiarly bright and compact peaks detected in all JWST bands. The knot is likely the most energetic example of a protostellar jet driven by a massive star impacting dense interstellar medium. The new images provide a complementary view to the previous long-wavelength perspective on this 4 x 8 pc area of one of the most active star-forming regions in our Galaxy, revealing new mysteries to be further explored.